That would be an interesting study. I’m agnostic, never been atheist – wasn’t my thing. Also, never had much of a need to thump my chest and yell I HAVE A PENIS EVERYBODY!.
I’m male, no question and never had an issue with gender identity but I never felt a need to assert gender identity much with others. So if it turned out that among non-believers, there were a higher percentage of agnostic among women than atheist among women, and a higher percentage of atheist among men and a smaller percentage of agnostic among men, that would be logical to me, from a subjective pov.